In the area of offshore oil extraction, collecting oil and gas extracted from wells in the bottom of the sea is made through horizontal conduits, in English flowlines, generally static, and mainly vertical conduits, in English risers, responsible for connection between horizontal conduits and the platform or ship for extracting oil. The vertical conduits can be of rigid or flexible types.
Notably, the flexible conduits (flexible risers) used for this purpose are exposed to different weather conditions arising from the environment in which they are inserted. The strong currents and the seawater itself require that flexible conduits be ready for all the adversities imposed on them.
For this purpose, the state of art foresees flexible conduits made of several layers of materials and in different ways. Among the layers present in the flexible conduit are at least an internal tensile armor and at least an external tensile armor superimposed in relation to said internal tensile armor, wherein each tensile armor is formed by helically winding of a plurality of wires, generally steel. The tensile armors are responsible for the tensile strength of the flexible conduit.
Due to the complexity of manufacturing the flexible conduits and the size of the coiled wire of the tensile armor used in this method, segments of flexible conduits of approximately 1,000 meters long are used over an oil collecting line. Thus, to achieve the required length of the collecting line according to its application, connectors at the ends of each segment of flexible conduit are installed in order to make the connection between the different segments of flexible conduits. Furthermore, the connectors are used to connect the end of a flexible conduit to a manifold station or a platform or a ship for oil extraction.
The connectors are responsible for supporting, accommodating and securing all layers of the flexible conduit, maintaining their internal and external sealing. When installing the connector on the flexible conduit, it is necessary to perform an anchorage of the internal tensile armor and external tensile armor near the connector. To perform this anchorage, one of the options consists in executing one conformation in each extremity of each tensile armor wire producing a terminal region formed into an anchoring profile, for example a corrugated form, as disclosed in U.S. Pat. No. 6,592,153. The shaped terminal regions of each wire are accommodated within the interior of an existing chamber in the connector, wherein said chamber are filled with epoxy resin, thereby making the anchoring of the tensile armor next to the connector.
The terminal region of each wire of each the tensile armor is conformed individually by an operator, with the aid of a shaping device, which requires intensive labor and time for installation of the connector on the flexible conduit. Furthermore, the plastic deformation conferred to the conformed terminal regions in the anchoring profile generates points with high residual stresses, which is characterized as tensile armor fatigue failure factor of the flexible conduits.
Other examples of anchoring of the tensile armor are described in the International application WO2012126999. Particularly, in one of the disclosed examples, in addition to the terminal region conformed in an anchoring profile, each tensile armor comprises a bi-conical shaped portion, which moves away radially from the longitudinal axis of the flexible conduit, from the entry point said tensile armor in the chamber, and then draws near radially the longitudinal axis of the flexible conduit, as said tensile armor approaches the connecting flange of the connector. This particular bi-conical shaped configuration of the tensile armor improves the anchoring performance of the tensile armor next to the connector.
To obtain this particular configuration of tensile armors, International application WO2012126999 teaches that first, each tensile armor wire must be moved outward radially from each wire of each tensile armor, then to introduce, under the outwardly moved parts of the internal tensile armor, a shaping ring having a bi-conical shaped external profile. Afterwards, each wire of tensile armor is moved over the shaping ring creating the bi-conical shape in the tensile armor. It should be noticed that in this step it happens a plastic deformation in each wire of tensile armor. Subsequently, it is performed a conformation in the terminal region of each tensile armor wire, thus producing a terminal region conformed into an anchoring profile. To remove the shaping ring, the ends of the tensile armor are lifted and then said ends are allowed to return to their initial position.
In practice, the method of producing the configuration of a tensile armor in a bi-conical shape, as taught in International application WO2012126999, increases even more the amount of labor and time necessaries for the installation of the connector on the flexible conduit, besides the fact that the plastic deformation attributed to the bi-conical shaped portion of tensile generates points with high residual stresses, which are characterized as a fatigue failure factor of the flexible conduit tensile armor.